It is well known in the prior art to produce an air cell cushioning dunnage product utilizing flexible thermoplastic sheet or film material and embossing one of the sheets, and applying a laminating or cover sheet or film thereto, for sealing formation of the air cells, with the product being utilized in cushioning applications. U.S. Pat. No. 3,416,984 dated Dec. 17, 1968 and entitled Method and Apparatus For Making Cellular Material From Thermoplastic Sheets is an example of such prior art.
In such patent, a heat sealable plastic sheet is heated to bring its outer surface to a temperature in the vicinity of the fusion temperature thereof, and is embossed on a vacuum drum, with the other surface of the embossed sheet being maintained at about the fusion temperature of the plastic, and then the laminating sheet is applied to the embossed sheet while the latter is on the embossing drum, with the surface of the laminating sheet which is to contact the embossed sheet being at a temperature above the fusion temperature thereof, so as that when the laminating sheet is applied to the embossed sheet, the contacting surfaces will equalize at a temperature at least equal to the fusion temperature thus adhering or sealing the films together.
U.S. Pat. No. 3,392,081 discloses an air cell cushioning product formed of multi-laminate film and wherein the areas of engagement between the embossed film and the laminating film are adapted to be in a fusable state when applied together, to form the closed air cells.
Moreover, there are considerable other patents in the air cell cushioning field, such as for instance Australian Pat. No. 160,551 published Oct. 29, 1953, and U.S. Pat. Nos. 3,018,015; 3,142,599; 3,231,454; 3,285,793; 3,349,990; 3,577,305; 3,389,534; 3,523,055; 3,575,781; 3,616,155; 3,785,899; 3,817,803; 3,837,990; 3,837,991; 3,868,056; 4,076,872; and 4,096,306.
In Applicant's copending U.S. patent application Ser. No. 75,662, now U.S. Pat. No. 4,314,865, filed Sept. 14, 1979 and entitled "Cushioning Dunnage Product, Apparatus and Method" there is disclosed a method and an apparatus for producing air cell cushioning dunnage which is formed from multi-stratum film of high density, high melting point, low density low melting point layers, and which include, a cooling step for cooling the product on the rotating forming drum to a particular temperature, prior to application of the laminating sheet to the embossed sheet on the drum.
The prior art methods and apparatus (other than Applicant's own as disclosed in aforementioned Pat. No. 4,314,865) are not generally of the type and size which can be readily and conveniently interrupted in operation and then restarted, without having considerable undesirable effects upon the resultant product, on the stock material utilized to produce the product, and/or the mechanism or apparatus per se; and such prior art does not teach an arrangement for cooling a heated embossed single stratum film on a rotatable forming drum and by means of such drum, to a predetermined temperature range prior to applying a heated laminating single stratum film thereto with associated pressure, for heat bonding the films together for sealing the air cells.